In recent years, thermosetting powder coating compositions which are usable without a solvent have been increasingly used from the viewpoints of prevention of environmental pollution and conservation of environment.
However, conventional thermosetting powder coating compositions generally have a drawback of giving a coating film which is unsatisfactory in the finished appearance.
To produce powder coating compositions which are free of such drawback and excellent in the finished appearance of coating film, the molecular weight of a vinyl copolymer used as the resin component of the composition has been lowered to reduce the viscosity of the coating composition thermally fused. Yet, the powder coating composition obtained in this way has posed a problem of being likely to cause blocking phenomenon that particles in the composition during storage weld together, thereby forming agglomerates.